196 MISC. PUBLICATION 243, U.S. DEPT. OF AGRICULTURE 
Culms simple or with a few simple branches. 
Blades firm, with sharp-cutting edges. 
Spikelets pubescent, at least toward the sum- 
mit; blades flat, more or less arcuate- 
Spence! 25 Sa 60. P.virGatTuM. 
Spikelets glabrous; blades V-shaped in cross 
section, ascending. 
Spikelets suborbicular, crowded; _ rachis 
ciliate. 
Panicle not pyramidal, the racemes rarely 
more than 50; glume and sterile 
lemma rather firm in texture. 
63. P. MILLEGRANA. 
Panicle elongate-pyramidal, the racemes 
commonly more than 70, short and 
crowded at the summit; glume and 
sterile lemma fragile. 
64. P. DENSUM. 
Spikelets obovate-elliptic; rachis not ciliate. 
Racemes slender; spikelets not crowded; 
rachis 0.7 mm wide__61. P. SECANs. 
Racemes thick; spikelets somewhat 
crowded; rachis 1 mm wide. 
62. P. ARUNDINACEUM. 
Plants not robust; if more than 1m tall, culms 
relatively slender. 
Spikelets 2 mm or more long. 
Spikelets about 3 mm long, pubescent. 
Blades 6 to 14 mm wide; spikelets oval. 
10. P. PUBIFLORUM. 
Blades very narrow, involute; spikelets 
lanceolate____38. P. ALTERNIFLORUM. 
Spikelets 2 to 2.6 mm long, glabrous. 
Spikelets broadest in the middle. 
Racemes 2 to 4, the rachis greenish, 1.2 to 
1.5 mm wide___-__- 37. P. ROCANUM. 
Racemes mostly 4 to 7, the rachis dark 
purple, 1.5 to 2 mm wide. 
11. P. LrvipuM. 
Spikelets broadest above the middle. 
Pedicels pubescent; spikelets 2.2 to 2.5 
mm long____36. P. PLEOSTACHYUM. 
Pedicels glabrous or scaberulous; spike- 
lets about 2 mm long. 
Spikelets subangular-obovate, 1.4 mm 
wide_____27. P. oLIGOSTACHYUM. 
- Spikelets obovate-elliptic, 1.1 mm wide. 
: 34. P. BAKERI. 
Spikelets less than 2 mm long. 
Spikelets glabrous, 1.6 to 1.9 mm long, oval. 
26. P. NESIOTEs. 
Spikelets more or less pubescent. 
Spikelets subhemispheric, 1.3 to 1.4 mm 
long, pubescent__28. P. PANICULATUM. 
Spikelets elliptic or oval. 
Racemes usually solitary, sometimes 2. 
46. P. SAUGETII. 
Racemes usually more than 2. 
Spikelets 1.3 mm long, oval, pubescent. 
30. P. BLODGETTII. 
Spiketets 1.5 to 1.8 mm long, or as much 
as 2 mm in P. larum. 
Primary pedicel nearly as long as the 
spikelet, the spikelets not 
crowded. ©»)24.8- 32. P. MOLLE. 
